this works perfect , but not as intended!
this makes a buzzer sound if your lights are on and the ignition is off, it is not effected by open/closed doors!
i know this isant as most peeps would like but its easy and available!
also this will only work if you have blade fuses as fitted to late 86ish 'c' reg vans on
this also only works if you have the 99 wiper relay fitted, not the 19 or no intermittent wipers.
basically what you need is the 292 relay as fitted to late caddys and from what i can see most late 90's on seats!
all you have to do is plug it into slot 7!
i have put this mod on several vans now without problems
this is the relay as it fits in the seat/caddy , so you know where to look. it sits out of the fuse box in its own little carrier!
e note!

this is the relay fitted to my van

i have put a pair of relays in the for sale section.